There is available online, a tool called Reaver [i dont wanna give here the download link] that it is capable of finding your wifi router password. This venerability is well known at least a year but now Researchers from Tactical Network Solutions in Maryland have announced a tool that is able to retrieve your wifi router's password and by that can unlock your network. BEWARE. If you use WPA/WPA2 passphrase then you can be exposed in 4-10 hours.
The vulnerability in WPS affects a large number of routers from a variety of manufacturers, including Cisco, Buffalo, D-Link and others.